The present invention relates to drainage systems. More particularly, the present invention relates to slot drains or line drains, which facilitate high capacity drainage of surface water or other liquid through a narrow linear slot, while ensuring a high drainage capacity.
Slot drains generally consist of cylindrical pipes or channels embedded beneath the surface to be drained with relatively narrow slots or throats extending upwardly from the pipe to the surface. Water present on the surface to be drained enters the throat through the opening in the surface and falls into the pipe or channel via which it is carried away to an appropriate drainage outlet, possibly via a silt box. The main advantage of slot drains is that, although the area of the drainage opening on the surface is small, the conduit along which the water is carried to the drainage outlet is large. This means that the drainage system can cope with heavy rainfall without requiring an excessive area of opening to be present. This is extremely important in some situations such as, for example, on roads and runways where surface water can be hazardous but where large drainage openings would be equally hazardous.
GB 2 311 549 discloses a slot drain in which the throat and channel are made from two pieces of steel, which are joined at the region of the base of the channel, each piece of sheet pressed steel forming one side of the channel and one wall of the throat. The hydraulic slot between the throat walls is formed by a series of spacer plates or separators that are welded to the throat walls and can extend the full depth of the throat. Restricted access tends to make the welding operating both tedious and time consuming. The separators are welded to the walls of the throat before the slot drain is galvanised and before being transported to the site at which the slot drain is to be used.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art.